1. Field of the Invention
The present invention relates to a control system for a motor-generator capable of functioning as a three-phase magnet-type synchronous motor after starting of an engine and functioning as a brushless DC motor before starting of the engine.
2. Description of the Related Art
To allow the motor-generator to function as the brushless DC motor before starting of the engine, it is necessary to detect a rotated position of a rotor included in the motor-generator to control the energization of a three-phase coil. In a conventional control system, a sensor such as a hall element and a photocoupler is used.
In a control system using a sensor such as a hall element and a photocoupler as in the prior art, it is difficult to fixedly dispose the sensor in proximity to the rotor of the motor-generator with a good accuracy. In addition, since wires for taking out a signal from the sensor are large in number and complicated and for this reason, the operation for assembling the motor-generator is complicated.
Accordingly, it is an object of the present invention to provide a control system for a motor-generator, wherein a rotated position of a rotor can be detected without use of a sensor, whereby the operation for assembling the motor-generator can be simplified.
To achieve the above object, according to the present invention, there is provided a control system for a motor-generator, comprising a rotated-position detecting means for detecting a rotated position of a rotor included in a motor-generator which is connected to an engine in such a manner that the motor-generator can function as a three-phase magnet-type synchronous motor after starting of the engine, and a control unit for controlling a DC power produced by rectifying an AC power from a commercial power source based on an output from the rotated-position detecting means and supplying the DC power to each of three-phase coils included in the motor-generator, the motor-generator being capable of functioning as a brushless DC motor before starting of the engine, wherein the rotated-position detecting means is arranged to detect an induced voltage in each of the three-phase coils included in the motor-generator and to detect a rotated position of the rotor based on the induced voltage.
With such arrangement, to allow the motor-generator to function as the brushless DC motor before starting of the engine, the rotated position of the rotor is detected by detecting the induced voltage in each of the three-phase coils. Therefore, a sensor such as a hall element and a photocoupler required in the prior art system is not required. Thus, it is possible to overcome the complexity of the assembling operation due to the use of the sensor and to simplify the operation for assembling the motor-generator.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings.